Undergraduate Research Journal

Effects of Dietary Phytoestrogens on Paternal
Responsiveness and Maturation in the
Biparental California Mouse
Aaron T. Stamp 1 , Trey Amador 2 , Breanna Harris 2 ,
Juan Pablo Perea-Rodriguez 2 , Wendy Saltzman 2
1
Department of Bioengineering
2
Department of Biology
University of California, Riverside
ABSTRACT
The California mouse (Peromyscus californicus) is a monogamous, biparental rodent in which
fathers show strong attraction to pups while virgin males show variable paternal responsiveness.
Previous studies have demonstrated that circulating testosterone enhances paternal behavior in
this species via aromatization to estrogen. We tested the hypothesis that paternal responsiveness
in virgin males would likewise be enhanced by dietary estrogens (i.e., phytoestrogens) from
soy. Virgin males (N=16 per group) were fed commercially available diets containing high,
medium, or low levels of soy from the time of weaning until sacrifice in early adulthood,
and behavioral responses to an unfamiliar pup, body mass, testis masses, fat-pad masses, and
epididymal sperm counts were compared among the three groups. No differences were found
in males’ behavioral responses to a pup. Similarly, testis masses, fat-pad masses, and sperm
counts did not differ as a function of dietary phytoestrogen content. However, changes in body
mass over time differed significantly among groups (P